This invention relates to a unipolar or multipolar electrical filter feedthrough device for an implantable electronic therapeutic device, e.g., a pacemaker. The filter feedthrough is designed to be introduced into an aperture of a housing of the therapeutic device, and comprises contact elements electrically separated from each other, a fixing means for harnessing the filter body around one wall of the housing as well as filter means that are, on one side, connectedxe2x80x94in an electrically conductive mannerxe2x80x94with one of the contact elements, and, on the other side, with the housing having a reference potential. The filter elements usually comprise capacitive elements. The contact elements are usually designed in the form of rod-shaped pins.
U.S. Pat. No. 4,152,540 describes a filter design for use with an electronic pacemaker, where a filter capacitor is introduced in a borehole in the insulation ceramic material.
Furthermore, European Patent publication EP 0 776 016 A2 reveals a filter design with a ceramic filter arrangement with capacities for implantable defibrillators and pacemakers. The filter arrangement is designed as a system of layers and is integrated in the particular device.
Another version known from the U.S. Pat. No. 5,650,016 and designed for use with implantable medical therapeutic devices comprises a filter constructed as a chip capacitor or an LC module and its integration with the device occurs through encapsulation.
However, the known electrical design versions have the disadvantage that the capacitive filter means as well as the contact areas between the electrical pins and the reference potential are made impermeable by a glass-seal. This resultsxe2x80x94especially taking into account the preassembly of the filter meansxe2x80x94in a substantial costs of manufacturing such a design version and of the introduction of the feedthrough device into the housing of the therapeutic device to be implanted, and its subsequent check for vacuum-tightness.
In addition, it is highly disadvantageous that the filter means are firmly connected with the feedthrough device and, therefore, exposed to a high thermal load when the feedthrough device is being welded into the aperture of the housing of the electronic therapeutic device. This requires a very firm mechanic binding of the filter means with the feedthrough device and, on the other hand, it often leads to an irreversible change in the electrical parameters of the filter means, which affectsxe2x80x94mostly in an unanticipated mannerxe2x80x94the operation of the therapeutic device to be implanted.
Based on the shortcomings of prior art, the task of this invention is, therefore, to describe a unipolar or multipolar design of the aforementioned feedthrough device that can be manufactured in an especially cost-effective manner, and can be installedxe2x80x94with a relatively low thermal load of the filter meansxe2x80x94in such a manner that a change of the electrical properties of the filter means during the assembly is excluded to a large degree.
This task is resolved by a filter design mentioned at the beginning, where the filter means are arranged outside the feedthrough device and connected with it in such a manner that, in installed condition, they basically stick out into the housing in a freely suspended manner.
The invention comprises the technical knowledge that the manufacture, assembly and vacuum leakage test of a unipolar or multipolar electrical feedthrough device with filter means after its installation in the housing of an implantable electronic therapeutic device can achieve special advantages if the feedthrough device and the electrical filter means are spatially arranged in a special manner, where a contact between the filter means and the housing wall is ensured and, at the same time, the basically non-vacuum-tight design of the used filter means need not be taken into account. This results in the advantage that the actual tightly closed element, i.e., the insulation ceramic material and its connections with the flange and the pins, can be tested for leakage tightness independently from the filter means.
According to this invention, the unipolar or multipolar electrical feedthrough device to be installed in an aperture in the housing of an implantable electronic therapeutic device comprises preferably flange-shaped fixing means that can be introduced in such an aperture and that are designed to connect the feedthrough device with the housing, and, furthermore, filter means designed as a capacitor, which are connectedxe2x80x94in an electrically conductive mannerxe2x80x94on the one hand, with electrical pins of the feedthrough device arranged in a from each other electrically separated manner, and, on the other hand, with the housing of the electronic therapeutic device having a reference potential, while the filter means themselves are arranged outside the feedthrough device. The filter means are connected with the feedthrough device in such a manner that they basically stick out into the housing in a freely suspended manner.
This results in a substantial advantage in that no requirements as for vacuum-tightness need to be made in relation to the filter means. Only the area of the housing, where the feedthrough device is introduced into the wall of the housing, and the feedthrough body itself must be designed in a vacuum-tight manner so that, after the therapeutic device has been implanted, no bodily fluid can enter the inside of the housing.
Another advantage is the decrease of thermal or mechanical load so that mechanical damage especially of the filter (which can not be detected or only to a limited degree) can be eliminated.
In a preferred design version according to this invention, the filter means form a filter block that is arranged on the same axis as the body of the feedthrough device. Such an arrangement results in simplification during the preassembly of the feedthrough device according to this invention.
The fixing means, designed to connect the feedthrough device with the housing of the therapeutic device to be implanted, and located on the feedthrough body, is preferably designed as a ring-shaped flange and is equipped with a metal collar extending towards the inside of the housing. The filter block is fastened at the free end of the collar without any physical integrity with the feedthrough body. The ring-shaped flange forms a sufficient buffer during the introduction of the feedthrough device into the housing aperture to allow a vacuum-tight welded connection between the feedthrough body and the housing wall. In order to achieve a stress-free connection between the feedthrough body and the filter block, i.e., a connection that is not mechanically stressed to an impermissible degree by the warmth released during the welding process, the metal collar is designed in a flexible manner. According to a preferred design version of this invention, such flexibility is achieved in a simple manner by making the metal collar of a band of lamellar structure. The lamellas are essentially uniformly arranged at the collar so that the collar has basically the shape of a crown.
During the preassembly of the feedthrough device, the filter block designed in a cylindrical shape is introduced into the space restricted by the crown-shaped collar. The shell of the filter block is then based on the inner side of the lamellas of the collar.
The contact between the lamellas and the shell of the filter block form an electrical connection between the individual filter elements assigned to each pin of the feedthrough device and the housing (with the reference potential) of the implantable electronic therapeutic device.
The filter block consists of a number of ceramic discs arranged over each other in a stack. This stack comprises a number of discs (corresponding with the same number of electrical pins) designed as metallized substrate discs and each located between two non-metallized ceramic layers in order to form capacitive filter elements of the filter block.
In order to form an electrical connection of the filter elements with the housing wall carrying the reference potential it is sufficient that each of the ceramic discs designed as a metallized substrate be connected with only one lamellas of the crown-shaped collar.
In another variant of this invention, the multipolar electrical feedthrough device comprises four electric pins so that the filter block consists of four disks designed as coated substrate and four ceramic disks without any coating, which formxe2x80x94arranged in an alternating mannerxe2x80x94the entire filter block.
An advantageous further variant of this invention comprises an additional connector pin to establish an electrical connection with the signal-generating and signal-processing unit of the electronic therapeutic device. This allows a simple connection of this unit with the reference potential.
In an advantageous design version of this invention, such a connection is designed in a band-wise manner, which results in special simplification of the preassembly of the signal-generating and signal processing unit.
Other advantageous design variants of this invention are characterized in sub-claims, and are described in detail in the following text by means of figures.